1. Field of the Invention
The present invention relates to an electronic flash device, particularly an electronic flash device in which the light quantity is controlled through comparison of the brightness of a main object and the brightness of a sub-object.
2. Description of the Prior Art
According to the conventional electronic flash device, the light quantity from a flash tube is measured by a light sensitive element, and the light quantity is controlled in correspondence to the output signal of the light sensitive element, and almost no consideration has been given to the natural light. Therefore, the conventional device has a defect that exposure errors occur during flash photograph under the presence of the natural light.
This defect has been solved by the device disclosed in U.S. Pat. No. 3,591,829 in which the light from the flash tube and the natural light are detected separately by an electronic filter, and the flashing of the flash tube is designed to stop when the total of the two lights reaches a predetermined value.
However, the device disclosed by U.S. Pat. No. 3,591,829 has a defect that proper exposure cannot be obtained for sub-objects which constitute the background of main objects such as personal figures and flowers, although proper exposure can be obtained for the main objects.